1. Field of the Invention
The present invention relates to a reclining apparatus switched to a locked state by meshing of internal teeth and external teeth.
2. Background Art
A description will be given using FIG. 11 and FIG. 12. FIG. 11 is a view showing a configuration of a seat and FIG. 12 is a side view of a reclining apparatus for vehicle seat in the related art.
As is shown in FIG. 11, a seat 101 is formed of a seat cushion 102 that supports the buttocks of a seat occupant and a seat back 103 that supports the back of the seat occupant. The seat back 103 is provided to be reclinable back and forth with respect to the seat cushion 102. A reclining mechanism 104 is provided on an axis of rotation for reclining of the seat back 103 to allow and inhibit the reclining of the seat back 103.
The reclining apparatus 104 will be described using FIG. 12. Referring to the drawing, a hinge pin 131 is provided to stand on a lower arm plate 130 to be installed on the seat cushion side. A ratchet plate 132 to be installed on the seat back side is provided to the hinge pin 131 in a rotatable manner. A recess portion having a circular-arc surface about the hinge pin 131 is formed at a bottom portion of the ratchet plate 132 and a plurality of internal teeth 133 are formed in the circular-arc surface in a circumferential direction.
A pole 134 is disposed between the lower arm plate 130 and the ratchet plate 132. A plurality of external teeth 135 that can mesh with the internal teeth 133 are provided to the pole 134 in a surface opposing the circular-arc surface of the ratchet plate 132.
On the other hand, the lower arm plate 130 is provided with guides 136 and 137 that guide the pole 134 in a radial direction of a circle about the hinge pin 131 from a locked position at which the external teeth 135 mesh with the internal teeth 133 to an unlocked position at which the external teeth 135 do not mesh with the internal teeth 133 and vice versa.
A release arm 142 provided to the hinge pin 131 in a rotatable manner is provided with a long hole 143 in which to engage a pin 140 of the pole 134 penetrating through an arc-like long hole 132e provided to the ratchet plate 132 about the hinge pin 131. A shape of the long hole 143 is set to have a portion close to the internal teeth 133 of the ratchet plate 132 and a portion remote from the internal teeth 133 for the pole 134 to move in the radial direction of the circle about the hinge pin 131 in association with rotations of the release arm 142, so that the external teeth 135 of the pole 134 mesh or do not mesh with the internal teeth 133 of the ratchet plate 132.
A first cam 144 is attached to the hinge pin 131 in a rotatable manner.
A second cam 141 is provided between a slope of the pole 134 on a side opposite to the side where the external teeth 135 are formed and the first cam 144. The slope of the pole 134 is a surface that crosses the radial direction of the circle.
The release arm 142 is given with a pushing force in a direction in which the first cam 144 presses the pole 134 via the second cam 141 by a spring 150 latched to the release arm 142 at one end and latched to the lower arm plate 130 at the other end.
Also, a groove is formed in an end face of the hinge pin 131. An inner end of a spiral spring 156 having an outer end latched to a pin 155 having an outer end provided to stand on the ratchet plate 132 is latched in this groove to push the ratchet plate 132 (upper arm) in a forward reclining direction.
An operation of the configuration above will now be described. A state shown in FIG. 12 is a state where the first cam 144 pushes the pole 134 via the second cam 141 that abuts on each of the slope of the first cam 144, the guide 137, and the pole 134 and the external teeth 135 of the pole 134 mesh with the internal teeth 133 of the ratchet plate 132, so that rotations of the ratchet plate 132 are inhibited to lock the reclining of the seat back 103.
When the release arm 142 located at a position indicated by a solid line is rotated to a position indicated by an alternate long and two short dashes line against a pushing force of the spring 150 in this state, the first cam 144 engaged with the release arm 142 starts to rotate in the same direction. Accordingly, the state where the first cam 144 pushes the pole 134 via the second cam 141 is released.
The pole 134 having the pin 140 engaged in the long hole 143 of the release arm 142 is also guided by the guides 136 and 137 and moves in the direction to the hinge pin 131. Accordingly, the meshing state of the external teeth 135 of the pole 134 and the internal teeth 133 of the ratchet plate 132 is released and the ratchet plate 132 (seat back 103) is switched to a reclinable state.
The seat occupant thus reclines the seat back 103 as he desires and releases an operation force of the release arm 142 when a desired reclining angle is obtained. Then, the release arm 142 returns to the position indicated by a solid line from the position indicated by an alternate long and two short dashes line due to a pushing force of the spring 150. The first cam 144 therefore rotates in an opposite direction to the direction of the last time and returns to the state of FIG. 12. An example is described, for example, in JP-A-08-019442.
However, tooth marks of a plurality of the external teeth 135 formed in the pole 134 are all, of a same shape. Hence, an angle yielded between tooth planes (planes of the external teeth 135 meshing with the internal. teeth 133) of the external teeth 135 at and near the end and a moving direction of the pole 134 becomes smaller.
When the seat occupant is reclining on the seat back 103, a load is transmitted to the pole 134 via the ratchet. plate 132. In this instance, a component force to the moving direction of the pole 134 becomes smaller for an input to the external teeth 135 at and near the end of the pole 134 from the internal teeth 133 of the ratchet plate 132. This raises a problem that releasing of the meshing state of the external teeth 135 of the pole 134 and the internal teeth 133 of the ratchet plate 132 (hereinafter, referred to as ease of coming off of the pole 134 from the ratchet plate 132) is deteriorated.